Process for in-situ deposition of a Ti/TiN/Ti aluminum underlayer

Abstract

A single chamber of a vapor deposition system is used to deposit both Ti and TiN. A Ti layer is deposited on the sample using a noncollimated process. N2 gas is then introduced in the chamber. A TiN layer is then deposited over the Ti layer. A second Ti layer is deposited over the TiN layer. A separate Ti pasting of a TiN chamber is eliminated, thereby increasing throughput. Further, only three physical vapor deposition chambers are used, thereby allowing the fourth chamber to be used for other metal deposition. Moreover, the second Ti layer eliminates the first wafer effect and reduces sheet resistance relative to a same chamber Ti/TiN underlayer. Lastly, the Al deposited on this new stack has a stronger <111> crystallographic texture, which leads to better electromigration resistance.

We claim: 
     
       1. A method for depositing Ti, TiN, and Ti, said method comprising the steps of: placing a sample in a single physical vapor deposition chamber, said chamber containing a Ti target;   introducing argon gas into said chamber at a selected flow rate;   depositing Ti on such sample in said chamber, said step of depositing Ti including applying a voltage across said target and said sample to generate a first plasma in said chamber;   terminating said plasma in said chamber by removing said voltage from across said target and said sample;   decreasing said flow rate of said argon gas;   introducing N 2  gas into said chamber to form TiN on said target;   depositing TiN, without removing said sample from said chamber, on said Ti deposited on said sample, said step of depositing TiN including generating a second plasma in said chamber;   removing said N 2  gas from said chamber; and   depositing Ti, without removing said sample from said chamber, on said TiN deposited on said sample; wherein said step of introducing N 2  gas comprises the step of introducing 70 to 90 SCCM of N 2  gas into said chamber.   
     
     
       2. A method for depositing Ti, TiN, and Ti, said method comprising the steps of: placing a sample in a single physical vapor deposition chamber, said chamber containing a Ti target;   introducing argon gas into said chamber at a selected flow rate;   depositing Ti on such sample in said chamber, said step of depositing Ti including applying a voltage across said target and said sample to generate a first plasma in said chamber;   terminating said plasma in said chamber by removing said voltage from across said target and said sample;   decreasing said flow rate of said argon gas;   introducing N 2  gas into said chamber to form TiN on said target;   depositing TiN, without removing said sample from said chamber, on said Ti deposited on said sample, said step of depositing TiN including generating a second plasma in said chamber;   removing said N 2  gas from said chamber; and   depositing Ti, without removing said sample from said chamber, on said TiN deposited on said sample,   wherein said step of depositing TiN comprises the steps of: introducing N 2  gas into said chamber; and   creating a plasma in said chamber between said target and said sample;     wherein said step of introducing N 2  gas comprises the step of introducing 70 to 110 SCCM of N 2  gas into said chamber; and   wherein said step of creating a plasma comprises the step of creating a plasma using at least 5000 W of power.   
     
     
       3. A method for improving the texture of an Al layer deposited on a sample, said method comprising the steps of: depositing a layer of Ti on a sample in a physical vapor deposition chamber;   depositing a layer of TiN on said Ti layer deposited in said Ti depositing step, said TiN deposition occurring in said physical vapor deposition chamber;   depositing a second layer of Ti on said TiN layer deposited in said TiN depositing step, said second Ti deposition step occurring in said physical vapor deposition chamber;   depositing a layer of Al on said second Ti layer deposited in said second Ti depositing step, whereby the volume fraction of <111> oriented grains of said Al layer is increased; and   depositing a second layer of TiN on said Al layer deposited in said Al depositing step, said second TiN layer for serving as an anti-reflective coating.